Much has been learned about earthquake engineering since the Bridge was designed and built in the 1930s. Today, mathematical analysis techniques help calculate how a structure will perform when subjected to various levels of ground shaking. In addition, physical tests are run on specimens that represent portions of the structure. Comparing and validating mathematical analysis with test results is a standard engineering method.

To test the strength of an existing bridge piece called a lattice strut on the Golden Gate Bridge, a large replica was made and tested by the University of California at Berkeley Civil and Environmental Engineering Department. A piece of that bent and buckled test specimen is displayed here. With accurate figures for the strength of these pieces, decisions can be made to replace or strengthen particular portions of the Bridge to preserve it against damage in future earthquakes.

The original lattice struts have a crisscross pattern of many small pieces of steel riveted together. When one of these struts is replaced, the new, stronger, one-piece steel member has holes cut in it to preserve the historic appearance of the Bridge.

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The U.C. Berkeley structural testing machine is three stories tall and can compress or push down on a specimen with a force of 4 million pounds (17.8 meganewtons).

credit: University of California at Berkeley

The replica of a steel lattice strut of the Bridge was tested in compression until it buckled, to measure its strength.

Photo by A. Astaneh-Asl (UC Berkeley)

All images property of the Golden Gate Bridge, Highway and Transportation District (unless otherwise indicated).